New Legs to Stand On

Reconstructing the past using ancient DNA

Jun 1, 2015

Mary Beth Aberlin

ANDRZEJ KRAUZEOrigin myths are foundational to the world’s cultures—depicted in cave paintings and later written or spoken. The fascination with origin stories lives on in modern humans, especially in a subgenre of such tales: how Homo sapiens got to be top dog. Dozens of print and film offerings inventively portray how the transition from tree-dweller to upright hominin might have played out—think Clan of the Cave Bear,The Ugly Little Boy, Iceman, Quest for Fire, and The Croods, to name but a few. Luckily, scientist debunkers are on the case.

Paleoanthropologist Ian Tattersall lays out the many factors, not least of which is our sometimes myopic fascination with our own species, that have complicated the drawing of any sort of reliable hominin evolutionary tree in an essay in this issue.

In the feature article “What’s Old Is New Again,” Senior Editor Bob Grant reports at length on how recent advances in sequencing ancient DNA, some from hominin leg bones more than 400,000 years old, will help prune or reshape such trees. The bugaboo for paleogenomics has been that the older the fossil sample, the more fragmented and degraded the DNA. But new techniques for extracting, purifying, and sequencing the stuff have allowed the piecing together of genomes from fragments just 30 to 35 base pairs in length, a development that may one day allow researchers to derive sequence data from million-year-old fossils and possibly nail down for good the hominin origin story.

The ancient-DNA revolution, in essence, offers powerful new tools for recreating the biological past, for humans and for other organisms whose genetic material is decently preserved due to favorable environmental conditions. And the new methods even have something to offer to forensic scientists, whose crime-scene collections often include similarly degraded DNA. Adios, creative alibis.

Origin stories clearly fascinate Wim Hordijk, a peripatetic, independent computational biologist who seeks to model the emergence of life from the basic chemistry present on early Earth. In “The Living Set,” Hordijk considers the possibility that life began through the formation of autocatalytic sets—self-sustain­ing networks of chemical reactions that create and are catalyzed by components of the system itself.

Before you read neuropsychologist Stuart Anstis’s feature “Seeing Isn’t Believing,” move the opening image up and down. What’s the neurological basis for the phantom movement you see? Anstis studies motion illusions and how they trick the visual system “because seeing the errors that a system makes can help us to understand how that system works nor­mally. Visual perception goes far beyond our retinal images, which provide only partial sensory information. We use our knowledge and expectations of the world to fill in the gaps,” he writes. You can read about the various illusions he and others have parsed, and then go to the-scientist.com and try them out yourself. Anstis’s research is helping to write the story about how our eyes and brains evolved.

We set two of this issue’s stories, “What’s Old Is New Again” and “A Plague on Pachyderms,” in motion with a pair of TS Live videos that will premiere on the-scientist.com this month. Humanity’s mythologies have monopolized the imagination for millennia, but as technological advances allow science to probe ever deeper into biology’s past, present, and future, those origin stories, and even early logic-based attempts at explaining our world, may need rewriting.